Despite removing the hot mirror of my mirrorless camera (a second-hand EOS M), the required exposure times were significantly longer than what I had anticipated. In my case, a proper exposure at noon required 1/30s at f/2.8, ISO 800. In contrast to that other people online were reporting much shorter exposure times such as 1/125 at f/8, ISO 100; 8 full stops shorter than my own.
It turns out that the dust reduction filter on interchangeable lens systems (i.e. DSLRs and mirrorless) also functions as a secondary IR filter. Thus, I had only removed one out of two filters on the camera.
the hot mirror which was removed
the dust reduction filter which was put back
Shortly after the half-assed attempt on mirrorless, I also converted a compact camera which has a fixed lens. Since compact cameras have no need for dust-reduction filters, I only had to remove the hot mirror for a proper full-spectrum conversion.
The glue removal was tedious, but there were significantly fewer steps required for disassembly, and the removal of the hot mirror itself is much less nerve-wracking compared to the EOS M.
Below sample shots for comparison. All of these were shot at 1/16s, f/2.8, ISO 800, fluorescent white balance.
EOS M, no modifications
EOS M, hot mirror removed, intact dust filter
Powershot S110, no modifications
Powershot S110, hot mirror removed, no dust filter by default
Comparing the EXIF data of the following sample shots, I'm seeing a difference of over 5 stops between the half-converted and fully converted cameras.
EOS M (1/30s, f/2.8, ISO 800)
Powershot S110 (1/100s, f/5.6, ISO 200)
The modified S110 camera has its own issues (namely, the lack of filter threads as well as being unable to achieve infinity focus when there is no IR filter in front of it). However, I think its compact size and built-in optical stabilization makes it a better all-around camera.
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